Molten salt hydrofining process

ABSTRACT

A PROCESS FOR CONVERSION OF HEAVY HYDROCARBON FRACTIONS CONTAINING HETERO-ATOM IMPURITIES COMPRISING CONTACTING THE FRACTIONS IN THE PRESENCE OF HYDROGEN, AT ELEVATED TEMPERATURE AND PRESSURE WITH A MOLTEN SALT COMPRISING CADMIUM HALIDES, AN ALKALI METAL HALIDE AND OPTIONALLY ONE OR MORE ADDITIONAL SALTS AS DILUENTS OR CO-CATALYSTS.

United States Patent 3,679,577 MOLTEN SALT HYDROFINING PROCESS CharlesF. Wantland, Pasadena, Tex., Frank E. Juge, Jr., Maitland, Fla., andWilliam H. Hinds, Houston, Tex., assignors to Shell Oil Company, NewYork, N.Y. No Drawing. Filed Nov. 29, 1968, Ser. No. 780,256 Int. Cl.C10g 13/08, 23/02, 29/12 US. Cl. 208-408 Claims ABSTRACT OF THEDISCLOSURE A process for conversion of heavy hydrocarbon fractionscontaining hetero-atom impurities comprising contacting the fractions inthe presence of hydrogen, at elevated temperature and pressure with amolten salt comprising cadmium halides, an alkali metal halide andoptionally one or more additional salts as diluents or cocatalysts.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a process for hydrofining heavy petroleum oils using a moltensalt catalyst mixture comprising cadmium halide, an alkali metal halideand optionally other metal salts as diluents and/ or co-catalysts.

Description of the prior art A steadily increasing demand for distillatepetroleum products and decreasing supply of crude oils of low residuecontent provides increasing incentive for processes which upgradehigh-boiling residual polynuclear hydrocarbon stocks. There areavailable large quantities of naphthenic, aromatic or mixed based crudesfrom which some distillate products are recoverably by traditionalmeans. However, the residual fraction, in which is concentratedrelatively large quantities of materials containing sulfur, oxygen,nitrogen, and organo-metallic compounds must be disposed of. In thepast, low-value stocks have been used for industrial and marine fuelsbut the supply exceeds demand. Moreover, air pollution restrictionsimposed on many industrial areas prevent the use of these high sulfurand nitrogen fuels.

Current technology for upgrading these fuels, such as thermal cracking,catalytic cracking, and catalytic hydrogenation are less thansatisfactory. Cracking or hydrogenation is relatively costly whenapplied to residual stocks due to rapid catalyst deactivation by thehigh content of contaminants and catalyst poisons found in residues.

The use of molten salt catalytic systems has long been recognized as amethod to obviate many of the difiiculties encountered in moreconventional refining techniques. In the main, previous work hasconcentrated on the use of molten caustics, such as sodium hydroxide,for example U.S. 3,051,645, issued August 1962. More recently, acidicmolten salt systems, such as zinc chloride, have been proposed forhydrocarcking (Gorin et al., US. 3,355,376, issued November 1967). Useof a molten salt catalyst offers many advantages over conventionalheterogeneous catalyst systems as, for example, continual renewal ofcatalyst surface, close temperature control by better and more uniformheat transfer and the possibility of continuous removal and relativelyeasy handling of contaminants, such as metals, which seriously interferewith catalyst performance in conventional heterogeneous phase catalyticsystems.

The use of acidic salt systems also presents a number of problems. Thesalt must have reasonably high catalytic activity and the ability toretain activity without sub- "ice stantial decline over a period of use.The hydrocarbons and salt should be easily separated and the salt shouldbe easily regenerated or otherwise restored for reuse aftercontamination or deactivation.

Th solubility of heavy hydrocarbons in some molten salt systems makesseparation difficult. This feature alone is a serious economic deterrentto proposed molten salt hydroconversion processes and represents a majordrawback of such systems.

We have now invented a process for hydrofining and/ or cracking heavypetroleum oils using a molten salt mixture possessing the requiredcharacteristics and advantages enumerated above. By hydrofining ismeant, within the context of the present invention, hydrogenation,desulfurization, denitrification, and metals removal.

SUMMARY OF THE INVENTION The process of the invention in broad aspectcomprises contacting heavy petroleum fractions with a molten saltmixture or solution comprising cadmium halide and other metal halides aslater specified, in the presence of hydrogen at elevated temperature andpressure.

The heavy petroleum fraction feed to the present process may be any highboiling hydrocarbon oil at least about 50% by volume of which boilsabove about 450 F. Though lighter hydrocarbons can, in principle, beprocessed, the present process is most advantageous for treatment ofoils containing materials which cannot be distilled in commercialequipment without extensive cracking, e. g., residual materials andhydrocarbon oils, containing asphaltenes, resins and the like. Theprocess finds its greatest utility in the treatment of stocks containingappreciable amounts of hetero-atoms and/or metals. It is, therefore,particularly useful for the treatment of reduced crudes, pitch, vacuumresidues, cracked gas oils, residues, and the like which cannototherwise be deeply flashed without excessive carryover of metalcontaminants. In addition, certain crude petroleum oils which containonly small amounts of gasoline and kerosene boiling-range hydrocarbonsand which have been topped to remove lighter components may also beprocessed. Certain petroleum crude oils from tar sands and oils fromshale or coal thus may be processed.

The metal salt catalyst of the invention comprises cadmium halide(chloride, bromide or iodide) which is mixed with and dissolved inalkali metal halides. Examples of suitable alkali metal halides arehalides (chlorides, bromides, or iodides) of lithium, sodium, andpotassium. additional metal salts as diluents or co-catalysts as, forexample, any mineral acid salt of metals of Group I, H, HI, IV-B, VI-B,VII-B, and VIH of the Periodic Table of Elements. The preferredco-catalytic additional salt is zinc halide. In general, at least about5% w. alkali metal salt should be contained in the mixture. The alkalimetal halide functions to reduce markedly the solubility of hydrocarbonin the salt melt, thus providing a mixture which can easily be separatedfrom the hydrocarbon feed and products, as for example, by phaseseparation. The pres ent process requires the use of an amount of moltensalt mixture in excess of that required for stoichiometric reaction withthe non-hydrocarbon elements of the heteroatom components in the feed,i.e., greatly in excess of that required for reaction with nitrogen,oxygen and sulfur in the feed. The invention lies in the catalyticeifect of the salt and not in the stoichiometric reactions whichconcurrently occur. The use of a relatively large excess of salt,relative to feed, characterizes one of the distinctions of the presentprocess over previously known process for hydrogenation ofhydrocarbonaceous material, such as coal, by impregnation of thematerial to be hydrogenated with a small quantity of metallic salt.

The process is carried out in the presence of hydrogen at elevatedtemperatures and pressures and is characterized by very short reactioncontact time.

Temperatures in the range of about 650-850 F. are used and preferably inthe range from about 750-810 F. Hydrogen pressures of between aboutSOD-5,000 p.s.i.g. shouldbe used-the total pressure depending, interalia, upon the purity of the hydrogen used. It is an especiallynoteworthy characteristic of the present invention that shown in TableI. From these data it can be seen that the salt mixtures containingcadmium halides eifectively increase API gravity (indicating lowermolecular weight), reduce the sulfur and nitrogen content of the feed,remove vanadium, and increase hydrogen content of the products. Runnumber N-ll illustrates that the absence of cadmium halide leads tothermal cracking only (note the negative hydrogen consumption denoting apositive hydrogen production) with little or no removal of sulfur,nitrogen or reaction contact time is very short. In general, a contact10 metals.

TABLE I.MOLTEN SALT REACTIONS Run Number Feed N-7 N-8 N-9 N-10 N-ll CdI2 (31.2) CdClz (80.0) CdIz 71.3) CdBrz (65. 4) L101 (45. 5 (Pmmt W9K01 (2o. K1 E28. 7 NaBl a4. 6 nor 54. 53 Temp., F... 5100' s00 566Pressure, p 2, 000 2, 000 2, 000 2, 000 2, 000 WHSV feed/gm salt/hr. 0.31 0. 19 0. 18 0. 23 0. 22 Hzloil (mole) 16. 6 16. 6 16. 6 l6. 6 16. 6Conversion, percent w.

00-4 39. 6 19. 0 24. 9 33. 7 23. 7 H; consumption, s.e.f.lbb1 667 254519 -428 API at 60 F 22. 9 34. 4 28. 0 31. 32. 7 28. 4 Sulfur, percentw 1. 82 1. 09 1. 31 1. 02 0. 95 1. 44 Tot N, p.p.rn 1. 500 950 1,400 9001,200 1, 500 Metals, (p.p.m.) V V 5) V 5) V 5) V 5) V (11) 1 5 ppm. isthe analytical senstlvity. time of between about 1.0 to 10 seconds issuflicient to EXAMPLE II V obtain the desired results. By contact timeis meant the time in which the feed and molten salt catalyst are .incontact in the reaction zone. Longer contact time may, of course, beused depending, inter alia, upon the specific nature of the feed (i.e.,boiling range, hetero-atom and metallic impurities), the degree ofconversion desired and the temperature and contact efliciency of thespecific reactor system employed.

. As inother hydroconversion processes, excess hydrogen is usuallyrecovered, at least in part, from the reaction zone efiluent andrecycled to the reaction zone together with additional makeup hydrogen.Pure hydrogen is not required and any suitable hydrogen-containing gaswhich is predominantly hydrogen can be used. For example, hydrogen-richgas containing on the order of about 70% v. or more hydrogen which isobtained from a catalytic reforming process can be used.

Various methods of contacting the hydrocarbon feed with the molten saltcatalyst may be employed. One simple method comprises merely passing thehydrocarbon into a molten salt bath. Various types of reactors may beused as will readily occur to those skilled in the art. Reactorsemploying a dispersed gas/liquid system have been found suitable.Reactors employing concurrent plugflow of the fluid (molten salt,hydrogen and hydrocarbon feed) with a high degree of gas-liquid andliquid-liquid contacting are especially useful. The process may beoperated continuously or batchwise but is most efliciently and desirablyconducted continuously in a short contact time plug-flow reactor system.

The following examples serve to further illustrate the practice andadvantage of the invention and are not to be construed as limitationsthereof.

'7 EXAMPLE I 'metal halide eificiently reduces hydrocarbon solubility.

Salt composition, operating conditions and results are The followingexperiments illustrate the hydrocracking potential of a molten saltsystem containing cadmium halide and zinc halide as co-catalysts. AStraight Run Residue (properties shown in Table II) was hydrocrackedTABLE II Run Feed N-22 4 N-23 znBn (80.0) ZnBr (80.0) Salt composition,(percent w.) CdB1'2 (15.0) NaBr (5.0) NaBr (20.0) Operating conditions:

Suliur, percent w 1. 82 0. 14 0. 42 Nitrogen, p.p.m.w 1, 500 25 72Vanadium, p.p.m 15 7 5 As these data show, the salt melt containingcadmium bromide produced significantly better sulfur and nitrogenremoval and was more effective in reducing heavy (900 F. plus)boiling-range materialat these conditions down to 1.6% w. basis feed.

These examples illustrate the potential of the process of the invention.Many ways of utilizing this process in conversion catalysts), and largeamounts of heavy fractions boiling above 900 F. is an increasingeconomic necessity. The process of the invention is a process useful forthat purpose. The process may be employed, for example, under mildconditions to remove metals and hetero-atom impurities making a productsuitable for further more conventional processing. On the other hand,the process is capable of extensive cracking directly (as shown inExample H) and may be so employed. Various combinations of suchoperation may be chosen depending on individual requirements.

We claim as our invention:

1. A process for the conversion of heavy hydrocarbon fractions having atleast 50% boiling above about 450 F. comprising contacting the fractionwith a molten salt mixture consisting essentially of cadmium chloride,cadmium bromide, or cadmium iodide dissolved in the alkali metalchloride, bromide or iodide corresponding to the cadmium salt in thepresence of added hydrogen at elevated temperatures and pressuresresulting in net hydrogen consumption.

2. The process of claim 1 wherein the mixture contains additional saltselected from the group of zinc chloride, zinc bromide, and zinc iodide.

3. The process of claim -1 wherein the temperature is in a range fromabout 650 to 850 F. and hydrogen pressure is in the range of 500-6000p.s.i.g.

References Cited UNITED STATES PATENTS 2,749,288 6/1956 Watkins 208l252,987,468 6/1961 Chervenak 208-213 3,355,376 11/1967 Gorin et al 208103,371,049 2/1968 Gorin et al. 252-413 DELBERT E. GANTZ, Primary ExaminerG. E. SCHMITKONS, Assistant Examiner U.S. CL X.R.

